Electrowetting display devices are rendered images in accordance with electrowetting or electrocapillary. Briefly, the free surface energy of some fluids is changed due to electric field effects such that distribution area of the fluids can thus change along with the electric field effects.
In general, the opaque ink of the electrowetting display device includes a composition having a dye. Since the outdoor operation requirements of display devices have gradually increased, the ink of the electrowetting display device must exhibit low driving voltage and high weathering resistance. The outdoor applications of the electrowetting display devices, however, are limited, due to inferior light resistance and thermal resistance of dyes.
An opaque ink including pigments for replacing the dyes has been developed. In order to ensure that electrowetting display devices can be operated under a low voltage, the pigments have to be in a nanoscale form.
The pigments with nanoscale particle sizes, however, are apt to be aggregated in accordance with the second law of thermodynamics, due to the increase of surface area and surface energy of the pigments. In order to uniformly disperse nanoscale pigments in the ink composition, the conventional ink composition has to increase the addition of a dispersant. Therefore, due to the high concentration of the dispersant, the viscosity of the ink composition is increased, resulting in a reduction in the responsiveness of the electrowetting display device.